wapbl_read
error = wapbl_read(data, slen, wr->wr_devvp, pbn);
error = wapbl_read(data, len, wr->wr_devvp, pbn);
error = wapbl_read(scratch, 2<<log_dev_bshift, devvp, pbn);
wapbl_read(scratch2,
int wapbl_read(void *, size_t, struct vnode *, daddr_t);